CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating Activities
Net earnings	$ 142,674,000	$ 8,484,000
Adjustments to reconcile net earnings to net cash provided by operating activities
Depreciation, depletion, accretion and amortization	141,314,000	135,108,000
Net gain on sale of property, plant & equipment and businesses	(911,000)	(6,624,000)
Contributions to pension plans	(4,737,000)	(2,822,000)
Share-based compensation	10,832,000	9,679,000
Excess tax benefits from share-based compensation	(23,749,000)	(11,457,000)
Deferred tax provision (benefit)	2,592,000	(11,656,000)
Cost of debt purchase	0	67,075,000
Changes in assets and liabilities before initial effects of business acquisitions and dispositions	(135,024,000)	(109,790,000)
Other, net	(30,458,000)	(13,360,000)
Net cash provided by operating activities	102,533,000	64,637,000
Investing Activities
Purchases of property, plant & equipment	(199,764,000)	(148,721,000)
Proceeds from sale of property, plant & equipment	2,427,000	3,419,000
Payment for businesses acquired, net of acquired cash	(1,611,000)	(21,387,000)
Decrease in restricted cash	1,150,000	0
Other, net	1,862,000	(334,000)
Net cash used for investing activities	(195,936,000)	(167,023,000)
Financing Activities
Proceeds from line of credit	3,000,000	284,000,000
Payments of line of credit	(3,000,000)	(145,500,000)
Payment of current maturities and long-term debt	(9,000)	(530,945,000)
Proceeds from issuance of long-term debt	0	400,000,000
Debt and line of credit issuance costs	0	(7,382,000)
Purchases of common stock	(69,156,000)	0
Dividends paid	(53,338,000)	(26,549,000)
Proceeds from exercise of stock options	0	50,769,000
Excess tax benefits from share-based compensation	23,749,000	11,457,000
Other, net	(1,000)	(1,000)
Net cash provided by (used for) financing activities	(98,755,000)	35,849,000
Net decrease in cash and cash equivalents	(192,158,000)	(66,537,000)
Cash and cash equivalents at beginning of year	284,060,000	141,273,000
Cash and cash equivalents at end of period	$ 91,902,000	$ 74,736,000